As methods of real-time communication performed via a network, there are not only chatting using text messages but also VoIP (Voice over Internet Protocol) and video phones using images and voices. For example, a conference with a number of people, or an English conversation lesson between a teacher and a student is commonly held using the function of video phones.
Patent Literature 1 discloses a technology relating to a screen display when a lesson or a conference is held in a virtual space. In addition, Patent Literature 2 discloses a technology of providing an asynchronous lesson in which each student can receive a lesson in an asynchronous manner based on teaching material data and a synchronous lesson in which students can receive a lesson while exchanging information with each other in a virtual space.